Polymer additives for powder coatings

ABSTRACT

Star polymers prepared by reacting a highly branched polymer and either a lactone or lactam are disclosed. These star polymers find particular application as additives for powder coating compositions, to improve various performance properties thereof. Powder coating composition comprising the described star polymers are also disclosed.

FIELD OF THE INVENTION

The present invention relates to polymers comprising a highly branchedpolymer to which is grafted linear moieties, and powder coatingscomprising the same.

BACKGROUND INFORMATION

In recent years, powder coatings have become increasingly popular;because these coatings are inherently low in volatile organic content(VOC), their use significantly reduces air emissions during theapplication and curing processes.

Powder coatings are typically cured by heating the coated substrate toan elevated temperature, such as higher than 125° C. During the curingprocess, the powder particles melt and spread, and the components of thepowder coating react. During this curing phase, gas can be generated andemitted. This gas generation, known as “outgassing”, can result inbubbles, craters and other defects in the cured coating. It is thereforedesired to have powder coatings with reduced outgassing. It is alsodesired to minimize or lower the temperature at which a powder coatingscure. This allows for powder coatings to be used on a wider variety ofsubstrates, and also results in reduced energy needs.

Powder coatings can also be difficult to handle. Improved flow and/orleveling when using powder coatings is therefore also desired.

SUMMARY OF THE INVENTION

The present invention is generally directed to polymers that are thereaction product of a highly branched polymer and either a lactone or alactam. The highly branched polymer is formed by step-growthpolymerization between a polyfunctional first monomer having a firstfunctional group and a polyfunctional second monomer having a secondfunctional group; the first and second functional groups react with eachother, but not themselves. Various monomers can be used to form thehighly branched polymer, depending on the end product desired.

The polymers of the present invention find particular application asadditives and/or film-forming resins for powder coatings. Powdercoatings employing the current compositions will often demonstrateincreased flexibility and may have increased toughness. The presentpowder coatings also may have improved flow and leveling characteristicsand decreased gassing as compared with other powder coatings.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to compounds that comprise thereaction product of a highly branched polymer having terminal functionalgroups and a lactone, wherein the highly branched polymer is thestep-growth polymerization reaction product of a polyfunctional firstmonomer having a first functional group and a polyfunctional secondmonomer having a second functional group, wherein the first and secondfunctional groups will react with each other but not themselves. Thereaction product of the highly branched polymer and the lactone issometimes referred to herein as the “star polymer”.

The present invention is also directed to compounds that comprise thereaction product of a highly branched polymer having terminal functionalgroups and a lactam, wherein the highly branched polymer is thestep-growth polymerization reaction product of a polyfunctional firstmonomer having a first functional group and a polyfunctional secondmonomer having a second functional group, wherein the first and secondfunctional groups will react with each other but not themselves. Thereaction product of the highly branched polymer and the lactam is alsosometimes referred to herein as the “star polymer”.

As used herein, the term “highly branched polymer” refers to an ungelledpolymer comprised of polyfunctional monomers, wherein at least one ofthe monomers has at least three functional groups. The present highlybranched polymers generally contain a mixture of linearly and fullybranched repeating units. This is in contrast to a dendrimer, whichcontains only fully branched repeating units without any linearlyrepeating units, and is also in contrast to linear polymers, whichcontain only linear repeating units without any branching.

As noted above, the highly branched polymers are prepared by step-growthpolymerization of two different polyfunctional monomers.“Polyfunctional” as used herein refers generally to monomers having twoor more functional groups; typically, monomers used according to thepresent invention will be di-, tri-, and/or tetrafunctional although theinvention is not so limited. The monomers used will typically have onlyone type of functionality; the monomers may contain one or moreadditional functionality, provided this additional functionality doesnot interfere with the formation of the highly branched polymer. Variouspolyfunctional monomers can be used depending on the desired endproduct. For example, an alcohol and carboxylic acid can be reacted toform a highly branched polyester; an amine and carboxylic acid reactedto form a highly branched polyamide or if an excess of amine is used, apolyamido amine; an isocyanate and an alcohol reacted to form a highlybranched polyurethane; and an amine and isocyanate reacted to form ahighly branched polyurea. It will be appreciated that only highlybranched polymers having terminal amine groups are suitable for reactionwith the lactam, i.e. the polyamide, the polyamido amine and thepolyurea. As noted, the appropriate monomers should be selected toobtain the desired highly branched polymer; in addition, the monomersshould be selected such that the functional groups on each of themonomers will react with each other, but not themselves. Mixtures ofmonomers can be used; e.g. two or more different alcohols and two ormore different acids.

The highly branched polymers used in the present invention have terminalfunctional groups. Theoretically, all of the terminal functional groupswill be the same. The type of terminal functional group will depend onthe starting monomers and the ratio of these monomers. For example, ahighly branched polyester can be prepared by reacting a polyfunctionalalcohol and a polyfunctional carboxylic acid; when the hydroxy groups ofthe alcohol are in excess, the polymer will have terminal hydroxygroups, but when the carboxylic acid functionality is in excess, theterminal functional group will be an acid. Terminal hydroxy or aminegroups are needed to initiate the ring opening polymerization of thelactones and terminal amine groups are needed to initiate the ringopening polymerization of the lactams. Typically, either the hydroxygroup from the polyfunctional alcohol or the amine group from apolyfunctional amine will provide the terminal functionality for thehighly branched polymers.

Any suitable polyfunctional monomers can be used according to thepresent invention. Examples of suitable alcohols include ethyleneglycol, propylene glycol, propane diol, butane diol, di(ethyleneglycol), tri(ethylene glycol), tetra(ethylene glycol), di(propyleneglycol), tri(propylene glycol), tetra(propylene glycol), glycerol,trimethylol propane (“TMP”), pentaerythritol,1,1,1-tris(hydroxymethyl)ethane, triethanolamine and the like.

Examples of suitable dicarboxylic acids include malonic,dimethylmalonic, succinic, glutaric, adipic, trimethyladipic, pimelic,2,2-dimethylglutaric azelaic, sebacic, suberic,1,3-cyclopentanedicarboxylic, 1,2-cyclohexanedicarboxylic,1,3-cyclohexanedicarboxylic, 1,4-cyclohexanedicarboxylic, phthalic,terephthalic, isophthalic, tetrahydrophthalic, hexahydrophthalic,2,5-norbornanedicarboxylic, 1,4-naphthalic, diphenic, 4,4′-oxydibenzoic,diglycolic, thiodipropionic, 4,4′-sulfonyldibenzoic, and2,5-naphthalenedicarboxylic acids. Anhydrides of any of the foregoingare also contemplated. Examples of suitable tricarboxylic acids include,but are not limited to, trimesic acid, trimellitic acid, pyromelliticacid, butanetricarboxylic acid, naphthalene tricarboxylic acids andcyclohexane-1,3,5-tricarboxylic acid. Mixtures of polycarboxylic acidcompounds can also be used.

Examples of suitable amines include diethylenetriamine,triethylenetetramine, tetraethylenepentamine, dipropylenetriamine,ethylenediamine, tris(2-aminoethyl)amine, aminobenzylamines,aminohydrazides, and the like. Mixtures of multifunctional amines canalso be used.

Examples of suitable isocyanates includebis(4-isocycanatocyclohexyl)methane, diphenylmethane diisocyanate,isophorone diisocyanate, toluene 2,4-diisocyanate, hexamethylenediisocyanate, m-tetramethylxylene diisocyanatic, 1,3-phenylenediisocyanate, and 4,4′-4″triphenylmethane triisocyanate. Mixtures ofmultifunctional isocyanates can also be used. The multifunctionalisocyanates useful for preparing the hyperbranched polymers of thisinvention include monomeric multifunctional isocyanates, multifunctionalisocyanate adducts and/or isocyanate-terminated prepolymers.

The highly branched polymers used according to the present invention areprepared through step-growth polymerization, also known as condensationpolymerization. As will be appreciated by one skilled in the art,step-growth polymerization involves the reaction between twopolyfunctional monomers. Any standard step-growth polymerizationtechniques can be used according to the present invention. The highlybranched polymers used according to the present invention are thereforedistinct from polymers formed from self-condensation of a polyfunctionalmonomer. Such self-condensation reactions typically involve the use of amonomer of type AB_(x), wherein X≧2. This results in a well-definedmaterial in which every molecule in the system, be it monomer orpolymer, will have exactly one A group and more than one B group. Boththe structure and function of these molecules are distinct from thoseused in the present invention.

Generally, the highly branched polymers are prepared by charging thereactants to a suitable reaction vessel and heating to a temperatureappropriate to the type of polymer being prepared. Condensation productsof the polymerization reaction, such as water in the case of polyesterformulation, are continuously removed during the polymerization topromote high levels of monomer conversion, which results inhyperbranching. The polymerization should be carried out underconditions that will avoid gelation and crosslinking; this isaccomplished through appropriate selection of monomer ratios, such asdescribed by the Carothers' equation (W. H. Carothers, Transactions forthe Faraday Society, Volume 32, Issue 39, 1936).

The highly branched polymers used according to the present inventionwill typically have a number average molecular weight of about 500 to10,000, such as 1,000 to 5,000, as determined by gel permeationchromatography using linear polystyrene standards.

The highly branched polymer having terminal functionality is thenfurther reacted with either a lactone or a lactam. The lactones andlactams can be substituted or unsubstituted. It will be appreciated thatlactides are specific lactones and are within the present invention.Particularly suitable lactones are epsilon-caprolactones, such as methylepsilon-caprolactone, a mixture of isomeric methyl caprolactones or amixture of isomeric methyl epsilon-caprolactones withepsilon-caprolactone. Other examples include but are not limited tooctanoic lactones, butyrolactones, valerolactones, gluconolactones,oxycyclotridecane-2-ones, and pentadeca-lactones. Examples of suitablelactams include epsilon-caprolactam, 2-azetidione, pyrrolidiones, andvalerolactams.

The lactone or lactam is attached or grafted to the highly branchedpolymer through the ring opening polymerization of the lactone or thelactam initiated by the terminal functional group of the highly branchedpolymer. The results of the grafting is the “star polymer” according tothe present invention. The grafting step is accomplished by charging thelactone or lactam to the reaction vessel and heating the mixture to atemperature suitable for the ring opening reaction, typically 80 to 250°C. An additional catalyst can also be added. As a result of the graftingprocedure, between 1 and 100 percent of the terminal functional groupson the highly branched polymer will have a linear polymer chaincomprised of at least one lactone or lactam molecule attached thereto.Typically, the large majority (i.e. greater than 90 percent, such asgreater than 95 percent or 99 percent or greater) of the groups will bereacted. The linear polymer chains comprised of at least one lactone orlactam molecule that become attached will have either a terminal hydroxyin the case of a lactone or a terminal amine in the case of a lactam.Thus, the star polymer itself also has terminal functionality. By usinga large excess of lactone or lactam molecules, the equal reactivity ofthe terminal groups on the highly branched polymer can force thegrafting to occur at ˜100% of the terminal groups. A 5 to 50 fold excessof lactone or lactam to terminal functional groups can be used as canabout a 20 fold excess.

The reaction between the hydroxyl groups on the highly branched polymerwith the lactone will result in opening of the lactone ring in thenormal manner to produce a hydroxyl terminated lactone, the other end ofwhich will be attached to the highly branched polymer. The hydroxylterminated lactone chain may react with further lactone molecules toproduce a hydroxyl terminated polylactone side chain. A “lactone chain”therefore refers to a hydroxyl terminated side chain that results from“ring opening” the lactone; a lactone chain according to the presentinvention can contain one or more lactone-derived units. In determiningthe ratio of lactone to highly branched polymer to use, considerationshould be given to the amount of lactone needed to give the desiredaverage lactone chain length. Generally, the lactone chain length may beincreased indefinitely. Typically, the lactone does not merelypolymerize on to a few hydroxyl groups of the highly branched polymer toproduce several long lactone chains but rather the lactone molecules aredistributed among a large number of hydroxyls. As noted above, typicallygreater than 90 percent, such as greater than 95 percent or even 99percent or greater of the terminal functional groups of the highlybranched polymer have a lactone chain attached thereto, although theinvention is not so limited. The amount of lactone added (expressed as aweight percentage of the total weight of the star polymer—both branchedpolymer and lactone side-chains) is typically from 10 to 95 percent,such as 65 to 95 percent. Lactone chains comprised of 2 to 50 lactoneunits are particularly suitable for use in powder coatings.

Similarly, lactam chains are formed by reaction with the terminal aminegroups of the highly branched polymer to result in a star polymer havingan amine terminated lactam, the other end of which will be attached tothe highly branched polymer. The amine terminated lactam may react withfurther lactam molecules to produce an amine terminated lactam chain. A“lactam chain” refers to an amine terminated side chain that resultsfrom “ring opening” the lactam; a lactam chain according to the presentinvention can have one or more lactam derived units. Typically, as withthe lactone, the lactam molecules will be widely distributed on thehighly branched polymer. Again, while 1 to 100 percent of the terminalfunctional groups on the highly branched polymer will have a lactamchain attached thereto, typically greater than 90 percent, such asgreater than 95 percent or 99 percent or greater will have a lactamchain. All of the disclosures above regarding the lactones and lactonechains apply to the lactam/lactam chains as well. Lactam chainscomprised of 2 to 50 lactam units are particularly suitable for use inpowder coatings.

The weight average molecular weight of the star polymer of the presentinvention will typically be about 5,000 to about 500,000, such about25,000 to 250,000, as determined by gel permeation chromatography usinglinear polystyrene standards. These star polymers are also characterizedby melting temperatures in the range of about 40 to about 65° C. In someembodiments, such as some of the polyester and/or polyamide embodiments,the star polymer of the present invention will exhibit a meltingtemperature, but not a glass transition temperature.

The star polymers described herein find particular application asadditives for powder coatings. Accordingly, the present invention isfurther directed to powder coatings comprising one or more of the starpolymers described herein and a film-forming resin.

Any resin that forms a film can be used according to the presentinvention, absent compatibility problems. A particularly suitable resinfor use in the present powder compositions is one formed from thereaction of a polymer having at least one type of reactive functionalgroup and a curing agent having functional groups reactive with thefunctional group of the polymer. The polymers can be, for example,acrylic, polyester, polyether or polyurethane, and can containfunctional groups such as hydroxyl, carboxylic acid, carbamate,isocyanate, epoxy, amide and carboxylate functional groups.

The use in powder coatings of acrylic, polyester, polyether andpolyurethane polymers having hydroxyl functionality is known in the art.Monomers for the synthesis of such polymers are typically chosen so thatthe resulting polymers have a glass transition temperature (“Tg”)greater than 50° C. Examples of such polymers are described in U.S. Pat.No. 5,646,228 at column 5, line 1 to column 8, line 7, incorporated byreference herein.

Acrylic polymers and polyester polymers having carboxylic acidfunctionality are also suitable for powder coatings. Monomers for thesynthesis of acrylic polymers having carboxylic acid functionality aretypically chosen such that the resulting acrylic polymer has a Tggreater than 40° C., and for the synthesis of the polyester polymershaving carboxylic acid functionality such that the resulting polyesterpolymer has a Tg greater than 50° C. Examples of carboxylic acidgroup-containing acrylic polymers are described in U.S. Pat. No.5,214,101 at column 2, line 59 to column 3, line 23, incorporated byreference herein. Examples of carboxylic acid group-containing polyesterpolymers are described in U.S. Pat. No. 4,801,680 at column 5, lines 38to 65, incorporated by reference herein.

The carboxylic acid group-containing acrylic polymers can furthercontain a second carboxylic acid group-containing material selected fromthe class of C4 to C20 aliphatic dicarboxylic acids, polymericpolyanhydrides, low molecular weight polyesters having an acidequivalent weight from about 150 to about 750, and mixtures thereof.This material is crystalline and is preferably a low molecular weightcrystalline or glassy carboxylic acid group-containing polyester.

Also useful in the present powder coating compositions are acrylic,polyester and polyurethane polymers containing carbamate functionalgroups. Examples are described in WO Publication No. 94/10213,incorporated by reference herein. Monomers for the synthesis of suchpolymers are typically chosen so that the resulting polymer has a highTg, that is, a Tg greater than 40° C. The Tg of the polymers describedabove can be determined by differential scanning calorimetry (DSC).

Suitable curing agents generally include blocked isocyanates,polyepoxides, polyacids, polyols, anhydrides, polyamines, aminoplastsand phenoplasts. The appropriate curing agent can be selected by oneskilled in the art depending on the polymer used. For example, blockedisocyanates are suitable curing agents for hydroxy and primary and/orsecondary amino group-containing materials. Examples of blockedisocyanates are those described in U.S. Pat. No. 4,988,793, column 3,lines 1 to 36, incorporated by reference herein. Polyepoxides suitablefor use as curing agents for COOH functional group-containing materialsare described in U.S. Pat. No. 4,681,811 at column 5, lines 33 to 58,incorporated by reference herein. Polyacids as curing agents for epoxyfunctional group-containing materials are described in U.S. Pat. No.4,681,811 at column 6, line 45 to column 9, line 54, incorporated byreference herein. Polyols, materials having an average of two or morehydroxyl groups per molecule, can be used as curing agents for NCOfunctional group-containing materials and anhydrides, and are well knownin the art. Polyols for use in the present invention are typicallyselected such that the resultant material has a Tg greater than about50° C.

Anhydrides as curing agents for epoxy functional group-containingmaterials include, for example, trimellitic anhydride, benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride,tetrahydrophthalic anhydride, and the like as described in U.S. Pat. No.5,472,649 at column 4, lines 49 to 52, incorporated by reference herein.Aminoplasts as curing agents for hydroxy, COOH and carbamate functionalgroup-containing materials are well known in the art. Examples of suchcuring agents include aldehyde condensates of glycoluril, which givehigh melting crystalline products useful in powder coatings. While thealdehyde used is typically formaldehyde, other aldehydes such asacetaldehyde, crotonaldehyde, and benzaldehyde can be used.

The film-forming resin described above is generally present in thepowder coatings of the invention in an amount greater than about 50weight percent, such as greater than about 60 weight percent, and lessthan or equal to 95 weight percent, with weight percent being based onthe total weight of the composition. For example, the weight percent ofresin can be between 50 and 95 weight percent. When a curing agent isused, it is generally present in an amount of up to 30 weight percent;this weight percent is also based on the total weight of the coatingcomposition.

It will be appreciated that the hydroxyl functionality that results fromthe lactone addition or the amine functionality that results from thelactam addition will react with one or more of the other components ofthe powder coating composition. For example, if the star polymer hashydroxyl functionality at the end of a lactone chain, a blockedisocyanate crosslinker and a hydroxy functional film forming resin canbe used.

It is also possible, according to the present invention, to modify thefunctionality that is present on the star polymer. For example, thehydroxy functionality that results from lactone grafting can beconverted to an acidic functionality, by reacting the hydroxy, forexample, with a cyclic carboxylic acid anhydride. This reaction can becarried out by charging the hydroxy functional star polymer to thereaction vessel and heating the mixture to a temperature suitable forthe ring opening of the cyclic anhydride, such as 80 to 150° C. In thismanner, the hydroxy functional star polymer is converted to an acidicfunctional star polymer. This conversion may be relevant in a systemwherein a curing agent that is reactive with a carboxylic acidfunctional group is desired rather than a curing agent that is reactivetoward a hydroxy functional group, such as in a system using triglycidylisocyanurate. Other moieties as desired by the user could also beintroduced through reaction with the terminal hydroxy or amine on thestar polymer. One embodiment of the present invention specificallyexcludes acrylic functionality or other compounds with double bondsbeing attached to the end of the lactone or lactam chain; in thisembodiment, a powder coating comprising the star polymer would not haveradiation curable moieties. Another embodiment specifically excludes theaddition of conductive or photographically useful moieties into thepolymer, such as onto the end of the lactone or lactam chain; in thisembodiment, a powder coating comprising the star polymer would not haveconductive or photographically useful moieties. Yet another embodimentspecifically excludes the addition of hydrolyzing moieties onto eitherthe highly branched polymer or the star polymer of the presentinvention; in this embodiment, a powder coating comprising the starpolymer would not have hydrolyzing moieties.

The additive of the present invention is typically present in thecurable powder coating composition in an amount ranging from 0.1 to 20weight percent, such as 1 to 10 weight percent, or about 5 weightpercent, with weight percent based on total weight of the coatingcomposition. As used herein, “curable coating composition”, “curedcoating composition” and like terms will be understood as referring to acomposition in which the components react with each other so as toresist melting upon heating. It will be appreciated that inclusion ofthe present additives or star polymers in the powder coatings of thepresent invention will result in at least one improvement to theperformance characteristics of the present powder coatings, such asimproved flow and/or improved leveling, decreased gassing, increasedflexibility, and/or improved appearance. Even slight improvements in anyof these characteristics is deemed an improvement according to thepresent invention. Moreover, gloss can be more easily varied with thecoatings of the present invention.

The powder coating compositions of the present invention may optionallycontain other additives such as waxes for flow and wetting, flow controlagents, such as poly(2-ethylhexyl)acrylate, degassing additives such asbenzoin and MicroWax C, adjuvant resin to modify and optimize coatingproperties, antioxidants, ultraviolet (UV) light absorbers andcatalysts. Examples of useful antioxidants and UV light absorbersinclude those available commercially from Ciba Specialty ChemicalsCorporation under the trademarks IRGANOX and TINUVIN. These optionaladditives, when used, can be present in amounts up to 20 percent byweight, based on total weight of the coating.

The compounds of the present invention, as well as any additionaladditives, can be added at any time during the formulation of the powdercoating. For example, curable powder coating compositions of the presentinvention can be prepared by first dry blending the film-forming resin,and any of the additives described above including the presentcompounds, in a blender, such as a Henschel blade blender. The blenderis operated for a period of time sufficient to result in a homogenousdry blend of the materials. The blend is then melt blended in anextruder, such as a twin screw co-rotating extruder, operated within atemperature range sufficient to melt but not gel the components. Themelt blended curable powder coating composition is typically milled toan average particle size of from, for example, 15 to 80 microns. Othermethods known in the art for preparing powder coatings can also be used.

In certain embodiment of the present invention, the star polymersthemselves comprise the film forming resin. In such embodiments, thecurable powder coating comprises the star polymer described herein and asuitable crosslinker. Such crosslinkers are described above or areotherwise known to those in the art. In these embodiments, the starpolymer may comprise 40 to 80 weight percent of the total composition.Additives and methods of manufacture described above or known to thoseskilled in the art can be used to prepare these powder coatings.

The powder coating compositions are most often applied by spraying, andin the case of a metal substrate, by electrostatic spraying, or by theuse of a fluidized bed. The powder coating can be applied in a singlesweep or in several passes to provide a film having a thickness aftercure of from about 1 to 10 mils, usually about 2 to 4 mils. Otherstandard methods for coating application can be employed such asbrushing, dipping or flowing.

Generally, after application of the coating composition, the coatedsubstrate is baked at a temperature sufficient to cure the coating.Metallic substrates with powder coatings are typically cured at atemperature ranging from 230° F. to 650° F. for 30 seconds to 30minutes.

In certain embodiments, the present coating compositions comprise starpolymers that are the reaction product of the highly branched polymerand lactone that has terminal hydroxy groups or whose terminal hydroxygroups have been converted to acid groups; the star polymers do not haveany additional moieties attached thereto. In certain embodiments thestar polymer used in the present coatings does not contain a UV curablemoiety, such as (meth)acrylate.

As used herein, unless otherwise expressly specified, all numbers suchas those expressing values, ranges, amounts or percentages may be readas if prefaced by the word “about”, even if the term does not expresslyappear. Any numerical range recited herein is intended to include allsub-ranges subsumed therein. Plural encompasses singular and vice versa.Also, as used herein, the term “polymer” is meant to refer to oligomersand both homopolymers and copolymers; the prefix “poly” refers to two ormore.

EXAMPLES

The following examples are intended to illustrate the invention, andshould not be construed as limiting the invention in any way.

Example 1

A highly branched polyester was prepared using the following procedure.One hundred parts by weight of trimethylol propane, 81.1 parts by weightof adipic acid, and 5.6 parts by weight dibutyl tin oxide were chargedto a round-bottomed glass flask equipped with a mechanical stirrer,nitrogen inlet tube, thermometer, steam jacket column, fractionatingcolumn, and a distillation head connected to a condenser and a receiver.The resultant mixture was heated to react in a nitrogen atmosphere. Atabout 107° C., water generated by the esterification process began to becollected. With continuous removal of water, heating continued to 200°C. The reaction was allowed to continue until water was no longer beinggenerated by the reaction, at which time the reaction product was cooledto ambient temperature.

To this highly branched polyester was added 2606.9 parts by weight ofε-caprolactone. The resultant mixture was heated to react in a nitrogenatmosphere at a temperature of 165° C. The reaction was allowed toprogress for four hours at that temperature.

The reaction product was then cooled, discharged and analyzed. Thedetermined acid value was 4.7 mg KOH/gram, and hydroxy value was 21.5 mgKOH/gram. Analysis of the polymer by GPC (using linear polystyrenestandards) showed the polymer to have an M_(w) value of 28,237, M_(n)value of 5,348, and an M_(w)/M_(n) value of 5.3. The melting temperaturewas determined to be 53.7 by differential scanning calorimetry, and noglass transition temperature was observed.

Example 2

A star polymer was prepared as generally described in Example 1, onlyusing 5.8 parts by weight dibutyltin oxide. To the star polymer wasadded 132.1 parts by weight of hexahydrophthalic anhydride. Theresultant mixture was heated to react in a nitrogen atmosphere at atemperature of 120° C. The reaction was allowed to progress until noanhydride groups were detected by infrared spectroscopy analysis of thematerial.

The reaction product was then cooled, discharged and analyzed. Thedetermined acid value was 25.9 mg KOH/gram, and hydroxy value was 12.4mg KOH/gram. Analysis of the polymer by GPC (using linear polystyrenestandards) showed the polymer to have an Mw value of 20,957, Mn value of6,668, and an Mw/Mn value of 3.1. The melting temperature was determinedto be 53.2 by differential scanning calorimetry, and no glass transitiontemperature was observed.

Example 3

A highly branched polyester was prepared using the following procedure.One hundred parts by weight of tris(hydroxyethyl)isocyanurate, 47.6parts by weight of isophthalic acid, and 4.4 parts by weight dibutyl tinoxide were charged to a round-bottomed glass flask equipped with amechanical stirrer, nitrogen inlet tube, thermometer, steam jacketcolumn, fractionating column, and a distillation head connected to acondenser and a receiver. The resultant mixture was heated to react in anitrogen atmosphere. At 100° C., water generated by the esterificationprocess began to be collected. With continuous removal of water, heatingcontinued to 220° C. The reaction was allowed to continue until waterwas no longer being generated by the reaction, at which time thereaction product was cooled to ambient temperature.

To this highly branched polyester was added 2053.3 parts by weight ofε-caprolactone. The resultant mixture was heated to react in a nitrogenatmosphere at a temperature of 165° C. The reaction was allowed toprogress for four hours at that temperature, at which time it wasallowed to cool to ambient temperature.

The reaction product was then cooled, discharged and analyzed. Thedetermined acid value was 7.7 mg KOH/gram, and hydroxy value was 14.4 mgKOH/gram. Analysis of the polymer by GPC (using linear polystyrenestandards) showed the polymer to have an M_(w) value of 25,618, M_(n)value of 4,998, and an M_(w)/M_(n) value of 3.1. The melting temperaturewas determined to be 53.4 by differential scanning calorimetry, and noglass transition temperature was observed.

Example 4

A highly branched polyurethane was prepared using the followingprocedure. 126 parts by weight of cyclohexyl dimethylol, 12.6 parts byweight of trimethylol propane, 113.5 parts by weight isophoronediisocyanate, and 48.6 parts by weight hexamethylene diisocyanate, and0.5 parts by weight dibutyl tin dilaurate were charged to around-bottomed glass flask equipped with a mechanical stirrer, nitrogeninlet tube, thermometer, and condenser. The resultant mixture was heatedto react in a nitrogen atmosphere. The reaction was initially carriedout at 85° C., and was continuously increased to 235° C. as needed tomaintain sufficient agitation. The reaction was allowed to continueuntil no isocyanate groups were detected by infrared spectroscopyanalysis of the material, at which time the reaction product was cooledto ambient temperature.

To this highly branched polyurethane was added 1359.5 parts by weight ofε-caprolactone, and 2.7 parts by weight tin octoate. The resultantmixture was heated to react in a nitrogen atmosphere at a temperature of165° C. The reaction was allowed to progress for four hours at thattemperature, at which time it was allowed to cool to ambienttemperature.

To this star polymer was added 27.5 parts by weight of hexahydrophthalicanhydride. The resultant mixture was heated to react in a nitrogenatmosphere at a temperature of 170° C. The reaction was allowed toprogress until no anhydride groups were detected by infraredspectroscopy analysis of the material.

The reaction product was then cooled, discharged and analyzed. Thedetermined acid value was 7.3 mg KOH/gram, and hydroxy value was 12.4 mgKOH/gram. Analysis of the polymer by GPC (using linear polystyrenestandards) showed the polymer to have an M_(w) value of 25,433, M_(n)value of 10,216, and an M_(w)/M_(n) value of 2.5.

Example 5

A highly branched polyamide was prepared using the following procedure.Seventy-one parts by weight of ethylene diamine and 75.7 parts by weightof trimellitic anhydride were charged to a round-bottomed glass flaskequipped with a mechanical stirrer, nitrogen inlet tube, thermometer,and condenser. The resultant mixture was heated to react at 240° C. in anitrogen atmosphere. The reaction was allowed to continue until the acidnumber was found to be less than 5.0 mg KOH/gram, at which time thereaction product was cooled to ambient temperature.

To this highly branched polyamide was added 1366.7 parts by weight ofε-caprolactam and 15.1 parts by weight of tin octoate. The resultantmixture was heated to react in a nitrogen atmosphere at a temperature of240° C. The reaction was allowed to progress for six hours at thattemperature.

Example 6

Samples 1 through 5 were prepared using the ingredients and amounts (ingrams) shown in Table 1. The samples were prepared as follows: Theingredients were weighed together and processed for ˜20 s in a Prismblender at 3500 rpm's. This premix was then extruded through a b&pProcess Equipment and Systems 19 mm, co-rotating, twin screw extruder at450 rpm's, at temperatures ranging from 100° C. to 115° C. The resultantchip was milled and classified to a median particle size of 30 to 50 μmon a Hosokawa Micron Powder Systems Air Classifying Mill I. The formulaswere then electrostatically sprayed using Nordson corona equipment ontocold rolled steel panels supplied by ACT Laboratories as B-1000 P60 DIW,nonpolished panels. Finally, the panels were baked in electric DespatchLAD series ovens. Samples were baked for a dwell time of 25 minutes at325° F. All testing was run at a dry film thickness of 2.5 to 3.0 mils.TABLE 1 Material Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 RUCOTE121¹ 359.1 346.0 332.9 339.0 318.9 Product from Example 1 — — — 35.070.0 Product from Example 3 — 35.0 70.0 — — Aminoplast Crosslinker² 70.070.0 70.0 70.0 70.0 Di-p-tolylsulfonimide 1.5 1.5 1.5 1.5 1.5 2,2,6,6-0.6 0.6 0.6 0.6 0.6 tetramethylpiperidinol Benzoin 3.0 3.0 3.0 3.0 3.0RESIFLOW PL-200³ 6.0 6.0 6.0 6.0 6.0 LICOWAX C⁴ 6.0 6.0 6.0 6.0 6.0THIXCIN R⁵ 20.0 20.0 20.0 20.0 20.0 Dibutylamine 0.6 0.6 0.6 0.6 0.6TiO₂ R706 220.0 220.0 220.0 220.0 220.0 Impact 60/50 160/160 160/160160/160 160/160 (direct/reverse)(in-lbs)⁶ MEK (50 double rubs)⁷ 4 4 4 44 Off-gassing thickness 6.6 8.5 9.4 7.8 11.6 (mils)⁸¹Standard durable 40 OH functional polyester, from Bayer Corporation.²Aminoplast crosslinker synthesized by the following method: Into afive-liter four-necked reaction kettle equipped with a thermometer, amechanic stirrer, a nitrogen inlet, and means for removing theby-product (methanol) were placed 1728.0 parts by weight of CYMEL ® 303,919.0 parts by weight of p-toluic acid, 706.9 parts by weight of1H-benzotriazole, and 2.4 part by weight of p-toluenesulfonic# acid. The mixture was heated to 145° C. and the temperature wasmaintained under nitrogen sparge while the methanol by-product wasremoved from the system. The reaction progress was monitored by samplingthe mixture for acid value measurements. The reaction was terminatedwhen the acid value was less than 30. The reaction mixture was allowedto cool slightly before being discharged from the reactor. The productthus obtained is a pale yellow solid product with a Tg of 44° C. as #measured by DSC.³Acrylic flow additive dispersed on silica, from Estron Chemical.⁴Ethylene bis(stearamide), from Clariant Additives.⁵Castorwax derivative, from Elementis Specialties.⁶Impact testing was run according to ASTM D 2794 using a Byk-GardnerFalling Dart Impact tester.⁷MEK resistance was run by rubbing a Q-tip soaked with methyl ethylketone back and forth across a panel (one double rub) 50 times and thenrating the resulting marks as follows: MEK rating system:0 No change1 Slight gloss loss around test area2 Barely detectable gloss loss in test area3 Barely detectable scuffing of test area4 Slightly detectible scuffing of test area5 Noticeable scuffing of test area6 Marring of test area7 Smearing of test areaReadings of 0-5 are generally regarded as acceptable.⁸Off-gassing was tested by spraying a panel so that the coatingincreased in thickness from top to bottom. The panel was baked at 350°F. for 25 minutes and the film thickness where pinholes and/or blistersbegan was recorded in mils. The higher the number, the more tolerant thecoating is to off-gassing. The error in the test is approximately ±1mil.

As can be seen in Table 1, Samples 2-5, which incorporated the additivesof the present invention, had greatly improved impact resistance andoffgassing as compared with Control Sample 1, which lacked the presentadditives.

The product prepared according to Example 1 was also incorporated intoan isocyanate system using the ingredients and amounts (in grams) shownin Table 2. The formulas were prepared in exactly the same fashion asstated for Table 1, except samples were baked for a dwell time of 23minutes at 380° F. TABLE 2 Material Sample 6 Sample 7 Sample 8 Sample 9Sample 10 Sample 11 URALAC P-1580⁹ 330.0 321.9 313.8 — — — CRYLCOAT690¹⁰ — — — 420.0 397.0 374.0 Product from — 30.0 60.0 — 30.0 60.0Example 1 VESTAGON 165.0 165.0 165.0 74.1 74.1 74.1 EP-B 1400¹¹ BUTAFLOWBT-71¹² 1.5 1.5 1.5 1.5 1.5 1.5 Benzoin 3.0 3.0 3.0 3.0 3.0 RESIFLOWPL-200³ 7.0 7.0 7.0 7.0 7.0 7.0 TiO₂ R706 225.0 225.0 225.0 225.0 225.0225.0 Impact 50/40 100/160 160/160 30/<20 60/20 160/160(direct/reverse)(in-lbs)⁶ Stretches, not cracks MEK (50 double rubs)⁷ 64 5 3 3 2⁹Superdurable 85 OH functional polyester from DSM Resins.¹⁰Superdurable 30 OH functional polyester from UCB Surface Specialties¹¹ε-Caprolactam blocked isophorone diisocyanate from Degussa CRM¹²71% Dibutyltin dilaurate on silica support, from Estron Chemical.

As can be seen in Table 2, the samples prepared with the presentadditives again had improved impact resistance and comparable if notbetter MEK resistance.

Samples 12-16 were prepared using the ingredients and amounts (in grams)shown in Table 3. The formulas were prepared in exactly the same fashionas stated previously except that Samples 12 and 13 were sprayed ontopanels supplied by ACT Laboratories as B-1000 P60 DIW, nonpolishedpanels which were first coated in the lab with P-590 electrocoatavailable from PPG Industries, Inc. Samples 14-16 were sprayed ontosimilar substrate supplied entirely by ACT Laboratories as APR 45254.The formulations were baked for a dwell time of 25 minutes at 375° F.TABLE 3 Material Sample 12 Sample 13 Sample 14 Sample 15 Sample 16CRYLCOAT 630¹³ 502.8 475.1 502.8 500.2 497.7 Product from Example 2 —56.0 — — — Product from Example 4 — — — 15.0 30.0Triglycidylisocyanurate¹⁴ 37.8 37.8 37.8 37.8 37.8 VESTAGON BF 1540¹⁵21.0 21.0 21.0 21.0 21.0 ACTIRON 32-057¹⁶ 1.4 1.4 1.4 1.4 1.4 Benzoin5.6 5.6 5.6 5.6 5.6 RESIFLOW PL-200³ 7.0 7.0 7.0 7.0 7.0 LICOWAX C⁴ 2.62.6 2.6 2.6 2.6 IRGANOX 1076¹⁷ 8.4 8.4 8.4 8.4 8.4 TiO₂ R706 84.0 84.0150.0 150.0 150.0 264-8143 Fastolux Green¹⁸ 7.6 7.6 Vynamon Blue G FW025¹⁹ 2.0 2.0 Colortherm 10 5.1 5.1 Yellow Iron Oxide²⁰ Impact(direct/reverse)(in- 50/50 100/100 40/<20 50/<20 70/40 lbs)⁷ MEK (50double rubs)⁸ 4 3 6 5 6¹³Superdurable 35 COOH functional polyester, from UCB SurfaceSpecialties.¹⁴Available from Vantico Inc.¹⁵Self-blocked isophorone diisocyanate, from Degussa CRM.¹⁶Dimethyl lauryl amine on silica support, from Synthron Inc.¹⁷Antioxidant, from CIBA Additives.¹⁸Available from Sun Chemical.¹⁹Available from Avecia Colours.²⁰Available from Bayer Chemicals.

Again, the use of the present additives gave improved impact and MEKresistance.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

1. A compound that comprises the reaction product of a highly branchedpolymer having terminal functional groups and a lactone, wherein thehighly branched polymer is the step-growth polymerization reactionproduct of a polyfunctional first monomer having a first functionalgroup and a polyfunctional second monomer having a second functionalgroup wherein the first and second functional groups will react witheach other but not themselves, and wherein the polymer is not apolyester.
 2. The compound of claim 1, wherein the first monomercomprises at least one amine and the second monomer comprises at leastone carboxylic acid.
 3. The compound of claim 2, wherein the aminecomprises ethylene diamine and the carboxylic acid comprises trimelliticanhydride.
 4. The compound of claim 1, wherein the first monomercomprises at least one isocyanate and the second monomer comprises atleast one alcohol.
 5. The compound of claim 4, wherein the isocyanatecomprises isophorone diisocyanate and the alcohol comprises trimethylolpropane.
 6. The compound of claim 1, wherein the first monomer comprisesat least one isocyanate and the second monomer comprises at least oneamine.
 7. The compound of claim 6, wherein the isocyanate comprises theisocyanurate of isophorone diisocyanate and the amine comprises ethylenediamine.
 8. The compound of claim 1, wherein the highly branched polymerhas a number average molecular weight of 500 to 10,000.
 9. The compoundof claim 1, wherein the terminal functional group is a hydroxy group.10. The compound of claim 1, wherein the terminal functional group is anamine.
 11. The compound of claim 1, wherein 1 to 100 percent of theterminal functional groups have a lactone grafted thereto.
 12. Thecompound of claim 11, wherein greater than 90 percent of the terminalfunctional groups have a lactone grafted thereto.
 13. The compound ofclaim 1, wherein the reaction product of the highly branched polymer andthe lactone has a weight average molecular weight of 5,000 to 500,000.14. The compound of claim 1, wherein the lactone comprisesepsilon-caprolactone.
 15. The compound of claim 1, wherein the reactionproduct of the highly branched polymer and the lactone comprises lactonechains comprising 1 to 50 lactone derived units.
 16. A compound thatcomprises the reaction product of a highly branched polymer havingterminal amine functional groups and a lactam, wherein the highlybranched polymer is the step-growth polymerization reaction product of apolyfunctional first monomer having a first functional group and apolyfunctional second monomer having a second functional group whereinthe first and second functional groups will react with each other butnot themselves.
 17. The compound of claim 16, wherein the first monomercomprises at least one amine and the second monomer comprises at leastone carboxylic acid.
 18. The compound of claim 17, wherein the aminecomprises ethylene diamine and the carboxylic acid comprises trimelliticanhydride.
 19. The compound of claim 16, wherein the first monomercomprises at least one isocyanate and the second monomer comprises atleast one amine.
 20. The compound of claim 19, wherein the isocyanatecomprises the isocyanurate of isophorone diisocyanate and the aminecomprises ethylene diamine.
 21. The compound of claim 16, wherein thehighly branched polymer has a number average molecular weight of 500 to10,000.
 22. The compound of claim 16, wherein 1 to 100 percent of theterminal functional groups have a lactam grafted thereto.
 23. Thecompound of claim 16, wherein greater than 90 percent of the terminalfunctional groups have a lactam grafted thereto.
 24. The compound ofclaim 16, wherein the reaction product of the highly branched polymerand the lactam has a weight average molecular weight of 5,000 to500,000.
 25. The compound of claim 17, wherein the lactam comprisesepsilon-caprolactam.
 26. A curable powder coating compositioncomprising: (a) a compound that comprises the reaction product of ahighly branched polymer having terminal functional groups and a lactone,wherein the highly branched polymer is the step-growth polymerizationreaction product of a polyfunctional first monomer having a firstfunctional group and a polyfunctional second monomer having a secondfunctional group wherein the first and second functional groups willreact with each other but not themselves; and (b) a crosslinker.
 27. Thecurable powder coating composition of claim 26, wherein the firstmonomer is at least one alcohol and the second monomer is at least onecarboxylic acid.
 28. The curable powder coating composition of claim 27,wherein the alcohol comprises trimethylol propane and the carboxylicacid comprises adipic acid.
 29. The compound of claim 26, wherein thefirst monomer comprises at least one amine and the second monomercomprises at least one carboxylic acid.
 30. The compound of claim 29,wherein the amine comprises ethylene diamine and the carboxylic acidcomprises trimellitic anhydride.
 31. The compound of claim 26, whereinthe first monomer comprises at least one isocyanate and the secondmonomer comprises at least one alcohol.
 32. The compound of claim 31,wherein the isocyanate comprises isophorone diisocyanate and the alcoholcomprises trimethylol propane.
 33. The compound of claim 26, wherein thefirst monomer comprises at least one isocyanate and the second monomercomprises at least one amine.
 34. The compound of claim 33, wherein theisocyanate comprises the isocyanurate of isophorone diisocyanate and theamine comprises ethylene diamine.
 35. The compound of claim 26, whereinthe highly branched polymer has a number average molecular weight of 500to 10,000.
 36. The compound of claim 26, wherein the terminal functionalgroup is a hydroxy group.
 37. The compound of claim 26, wherein theterminal functional group is an amine.
 38. The compound. of claim 26,wherein 1 to 100 percent of the terminal functional groups have alactone grafted thereto.
 39. The compound of claim 38, wherein greaterthan 90 percent of the terminal functional groups have a lactone graftedthereto.
 40. The compound of claim 26, wherein the reaction product ofthe highly branched polymer and the lactone has a weight averagemolecular weight of 5,000 to 500,000.
 41. The compound of claim 26,wherein the lactone comprises epsilon-caprolactone.
 42. The compound ofclaim 26, wherein the reaction product of the highly branched polymerand the lactone comprises lactone chains comprising 1 to 50 lactonederived units.
 43. The curable powder coating composition of claim 26,further comprising a film forming resin.
 44. The curable powder coatingcomposition of claim 43, wherein the film forming resin is hydroxyfunctional.
 45. The curable powder coating composition of claim 43,wherein the film forming resin is present in an amount of 50 weightpercent or greater, based on total weight of the composition.
 46. Acurable powder coating composition comprising: (a) the reaction productof a highly branched polymer having terminal amine functional groups anda lactam, wherein the highly branched polymer is the step-growthpolymerization reaction product of a polyfunctional first monomer havinga first functional group and a polyfunctional second monomer having asecond functional group wherein the first and second functional groupswill react with each other but not themselves; and (b) a crosslinker.47. The compound of claim 46, wherein the first monomer comprises atleast one amine and the second monomer comprises at least one carboxylicacid.
 48. The compound of claim 47, wherein the amine comprises ethylenediamine and the carboxylic acid comprises trimellitic anhydride.
 49. Thecompound of claim 46, wherein the first monomer comprises at least oneisocyanate and the second monomer comprises at least one amine.
 50. Thecompound of claim 49, wherein the isocyanate comprises the isocyanurateof isophorone diisocyanate and the amine comprises ethylene diamine. 51.The compound of claim 46, wherein the highly branched polymer has anumber average molecular weight of 500 to 10,000.
 52. The compound ofclaim 46, wherein 1 to 100 percent of the terminal functional groupshave a lactam grafted thereto.
 53. The compound of claim 46, whereingreater than 90 percent of the terminal functional groups have a lactamgrafted thereto.
 54. The compound of claim 46, wherein the reactionproduct of the highly branched polymer and the lactam has a weightaverage molecular weight of 5,000 to 500,000.
 55. The compound of claim47, wherein the lactam comprises epsilon-caprolactam.
 56. The curablepowder coating composition of claim 26, further comprising a filmforming resin.
 57. The curable powder coating composition of claim 43,wherein the film forming resin is hydroxy functional.
 58. The curablepowder coating composition of claim 43, wherein the film forming resinis present in an amount of 50 weight percent or greater, based on totalweight of the composition.
 59. The curable powder coating composition ofclaim 26, wherein said coating composition does not contain moietiescurable by UV radiation.
 60. The curable powder coating composition ofclaim 46, wherein said coating composition does not contain moietiescurable by UV radiation.